Spark gap device



June 1, 1965 E. LINKROUM SPARK GAP DEVICE Filed oct. 2, 1961 United States Patent O anemie' SPARK GAP DEVICE Irving E. lbinhroum, Hancock, NX., assigner to The Bendix Corporation, Sidney, NX., a corporation oi' Eeiaware Fiied @et 2, 1961, Ser. No. 142,197 4 Claims. (Si. 313-193) This invention relates to a spark gap device, and more particularly relates to a spark gap device wherein the discharge across a first or main gap is triggered by a second gap of the spark gap device.

The invention has among its objects the provision of a novel triggered spark gap device.

A further object of the invention lies in the provision of a triggered spark gap device employing a gas lilled envelope enclosing the spark gaps of the device.

Another object of the invention is the provision of a triggered spari; gap device of the type indicated, the device employing two spark gaps having different breakdown voltages, the gap for the lower breakdown voltage serving as the triggering gap.

A still further object of the invention is the provision of a triggered spark gap device of the type indicated in the paragraph immediately above, wherein the triggering gap is shunted by an electrically semi-conductive material.

Other objects of the invention include the provision of a triggered spark gap device which is economically made, which may be accurately adjusted as to the breakdown voltage value of the triggering gap, and is reliable in its operation.

The above and further objects and novel features of the invention will more fully appear from the following description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only, and are not intended as a deiinition of the limits of the invention.

In the drawings, wherein like reference characters refer to like parts throughout the several views,

FIG. 1 is a view in elevation of an illustrative spark gap device made in accordance with the present invention;

FIG. 2 is a View in end elevation of the device of FG. l, the view being taken in the direction from right to left in FIG. l;

FIG. 3 is a view in longitudinal axial section through the spark gap device, the section being taken along the line 3-3 of FIG. 2, certain of the parts being shown in elevation;

FIG. 4 is a view in transverse section through the spark gap device, the section being taken along the line 4 4', of FIG. 3; and,

FlG. 5 is an enlarged fragmentary view of the spark gap device, such ligure particularly showing the shunted triggering gap of the device.

A triggered spark gap of the present invention may be employed to advantage in a number of different applications. One such application is in a circuit wherein stored energy is suddenly released upon the reception of a triggering signal. A circuit of this type is disclosed and claimed in the application of Segall, Blackington, and Knak, Serial No. 139,713, filed September 21, 1961, such circuit being disclosed for use in controlling stage separation and function initiation of multi-stage missiles.

rifurning now to the drawing, the illustrative spark gap device is generally designated by the reference character 10. Such device has a gas-impervious envelope formed of a metal disc 11 at its right hand, a metal disc 14 at its left hand, right and left glass tubes and 16, respectively, and an outer portion of a disc-like metal member 12 interposed between the inner ends of glass tubes 15 and 16. As shown, the end closure members and the sidewall forming members of the envelope are disclosed coaxially and are secured and sealed together by annular zones 17, wherein the ends of the glass tubes are fused and bonded to the adjacent metal pieces. Elements 11, 12, and 14 are made of metal having a coeiiicient of thermal expansion closely approximating that of the glass tubes 15 and 16. Elements 11, 12, and 14 may be made, for example, of the alloy known as Kovar, and glass tubes 15 and 16 may be made of Corning Glass No. 7052.

Secured to the end closure member 11 and projecting axially inwardly of the envelope is a first electrode generally designated 19, such electrode having a stem-like member 20, a flange 21 adjacent the base of the electrode, and an axially directed outer stem portion 22. Stern portion 22 extends outwardly through a central hole 24E- in element 11. Electrode 19 may be preliminarily secured to element 11 by being staked thereto at the outer end of the opening 24 and by being welded or brazed thereto at an annular zone 25 around tiange 21. Electrode support 26 has a bore therein extending from its outer end, the bore being threaded at 26 for the reception of a conductor-securing terminal thereto. The inner end of stem 2d is headed at 27. The electrode proper, designated 39, is in the form of a tungsten disc which is brazed to a head 27 by means of an interposed copper disc 29.

The left-hand electrode 31 is generally similar to electrode 19. The stem-like portion 32 of electrode 31 has a flange 34 at its root and an extension 33 of the stem therebeyond, parts 33 and 34 being secured to end wall 14 by being staked and brazed thereto, respectively. Part 32 has a threaded bore extending thereinto from the outer end thereof for the reception of a terminal to which another conductor of a circuit is to be connected. Member 32 is headed at 35, the second main electrode proper being in the form of a tungsten disc 37 secured to head by being brazed thereto through the medium of an interposed copper disc 36. In the embodiment shown electrodes 3@ and 37 have at least substantiaily the same diameter.

The intermediate metal disc-like member 12 functions as a third electrode in the envelope. Member 12 has an axially thinner central circular portion 4t) which is bounded by a circular sidewall 39. Portion 40 somewhat exceeds electrodes 30 and 37 in diameter. Projecting centrally through portion 4) of member 12 is an opening 41 which has a diameter somewhat less than that of electrodes 30 and 37. Telescoped over the head portion of electrode 31 is a ceramic sleeve member 42 which functions to space electrodes 37 and d@ and which also .serves to provide support for an electrically semiconductive material shunting the gap between electrodes 37 and 40.

Ceramic member 42 may be made, for example, of sintered alumina. Such member vhas a main tubular portion 44, which is telescoped over the head of electrode 31, and an inwardly directed annular flange 45 which overlies the edge portion of electrode 37 and is interposed between such electrode and the central electrode di?. As shown more clearly in FIG. 5, the axially inner end of member 42 is provided with a coating 47, the inner edge of flange 45 is provided with a coating 4d, and the surface of flange 45 overlying electrode 37 is provided with a coating 49. Such coating portions are integrally connected and, when the ceramic member 42 is mounted as shown in FIG. 3, form an electrically semiconductive path between electrodes 37 and 40.

The coating made up of portions de, 47, and 49 may be, for example, of the type disclosed and claimed in the anemie U patent to Harris, No. 2,953,704, September 20, 1960. Such semi-conductive material is formed of a mixture of 62E-98% by weight cuprous oxide and 232% by weight ferrie oxide, such mixture being sintered to the ceramic member 42.

The spark gap device I0 is completed by an exhaust tube 50 having an outer portion 5I projecting axially from end closure member lll. The inner end of tube 50 is necked in at 52, Such smaller diametered portion extending through a hole S4 in member 11, the tube being sealed to such member as by a brazed joint indicated at 55.

Electrical connection to the intermediate electrode 40 may be effected as by means of a clamp member 56, schematically shown in FIG. 3, which engages the peripheral edge of member I2. In preparing the device I0 for use, the interior of the envelope is first exhausted of air, following which it is lled with a mixture of gas composed of 80% by weight hydrogen and 20% by weight argon. With the electrodes 19 and 31 connected to a test circuit and with the tube 50 connected to the source of such mixture of gases under pressure, the pressure of the gas within the envelope is adjusted to such value that a spark discharge between main electrodes I9 and 31 occurs only when the voltage applied between such electrodes reaches a predetermined desired value. The spacing between the confronting end portions 30 and 37 of the electrodes, which affects the breakdown voltage of the main gap, will, of course, have been accurately set at a desired value during the manufacture of device I0. In the circuit of the above-referred-to Segall et al. application, for example, such voltage is 2,000` volts. After such condition of the spark gap device has been reached, the tube S0 is pinched off, welded, and severed to form the sealed closed end thereof designated 57 in FIG. l.

Under conditions of use, such as those described, the application of a triggering voltage of the requisite minimum value to electrodes 31 and 40 will cause a preliminary discharge across the triggering gap formed by such electrodes. The initial breakdown of such gap is aided by the presence of the semi-conductive material which shunts it. The breakdown of the triggering gap causes ionization of the gas molecules adjacent thereto, thereby immediately causing the breakdown of the second gap, between electrodes 3b and 37, since the gaseous ions have free access thereto through opening 4I. The triggered spark gap is thus positive and fast in its operation, discharge of gap 30, 37 following immediately after discharge of the triggering gap 37, dll.

Although only one embodiment of the invention has been illustrated in the accompanying drawings and described in the foregoing specification, it is to be expressly undersood that various changes, such as in the relative dimensions of the parts, materials used, and the like,

as well as the suggested manner of use of the apparatus of the invention, may be made therein without departing from the spirit and scope of the invention as will now be apparent to those skilled in the art.

Thus the member ldmay itself be made entirely of electrically semi-conductive material, rather than being provided with a semi-conductive coating on the portion thereof shunting the discharge gap between electrodes 37 and 41, as shown. Further, the member d4 may be made entirely of electrically insulating material and not be provided with a semi-conductive coating, when only the advantages of such member 44 resulting from the accurate spacing of electrodes 37 and 41 afforded by flange 45 and those of spark discharge along a surface (the radially inner surface of flange 45) are desired. Also, to provide a secure attachment of member 44 to the electrode made up of parts 3S, 36, and 37, the axially outer radially inner surface of the bore in member 454 may be metallized, and a brazed joint provided between such metallized surface and part 35.

What is claimed is:

ll. In a spark gap device, two axially aligned insulating tubes, a metallic center plate interposed between and sealed to adjacent ends of said tubes, two metallic end plates extending across and sealed to the remote ends of said tubes, each of said plates having a central open* ing therein, end electrodes supported by and extending inwardly toward each other from said end plates into spaced relation with opposed faces of said center plate in alignment with the opening in the latter, said electrodes comprising stem portions filling the openings in and sealed to said end plates, and a tubular sleeve closely surrounding the inner end portion of one of said end electrodes and having an internal flange projecting between and spacing the peripheral marginal portion of the inner end face of said one end electrode from the adjacent face of said center plate around the opening therein, the internal surface of said flange and the internal surface of the opening in said center plate being in substantial registry, whereby said internal surface of the flange constitutes a shunting surface between the inner face of said one end electrode and said center plate.

2. A spark gap device as defined in claim I, wherein said shunting surface is coated with an electrically semiconductive material.

3. A spark gap device as defined in claim l wherein said sleeve is constituted at least in part of an electrically semi-conductive material.

4. In a spark gap device, two axially aligned insulating tubes, a metallic center plate interposed between and sealed to adjacent ends of said tubes and having a central opening therein, two metallic end plates exten-ding across and sealed to the remote ends of said tubes, end electrodes supported by and extending inwardly toward each other from said end plates to form a spark gap between the adjacent inner end faces thereof, and a tubular sleeve closely surrounding the inner end portion of one of said end electrodes and having an internal flange projecting between and spacing the peripheral marginal portion of the inner end face of said one end electrode from the ad jacent face of said center plate around said opening, the internal surface of said ange and the internal surface of said opening being in substantial registry, whereby said internal surface of the flange constitutes a shunting surface between the inner face of said one electrode and said center plate.

References Cited by the Examiner UNITED STATES PATENTS 1,634,627 7/27 Osborn 313-249 2,367,332 1/45 Bondley 313-249 X 2,617,958 11/52 Stutsman 313-193 X 2,698,402 12/54 Graham et al. 315-36 2,870,376 1/59 Tognola 313-131 X ARTHUR GAUss, Primary Examiner. 

1. IN A SPARK DEVICE, TWO AXIALLY ALIGNED INSULATING TUBES, A METALLIC CENTER PLATE INTERPOSED BETWEEN AND SEALED TO ADJACENT ENDS OF SAID TUBES, TWO METALLIC END PLATES EXTENDING ACROSS AND SEALED TO THE REMOTE ENDS OF SAID TUBES, EACH OF SAID PLATES HAVING A CENTRAL OPENING THEREIN, END ELECTRODES SUPPORTED BY AND EXTENDING INWARDLY TOWARD EACH OTHER FROM SAID END PLATES INTO SPACED RELATION WITH OPPOSED FACES OF SAID CENTER PLATE IN ALIGNMENT WITH THE OPENING IN THE LATTER, SAID ELECTRODES COMPRISING STEM PORTIONS FILLING THE OPENINGS IN AND SEALED TO SAID END PLATES, AND A TUBULAR SLEEVE CLOSELY SUR- 